Spraying head

ABSTRACT

A spraying head for the humidification of intake air, especially the intake air of a piston engine, said spraying head comprising a body and a channel for supplying a spraying medium from an inlet to at least one nozzle. The spraying head ( 6 ) is provided with at least two channels ( 18, 18′, 18 ″), each forming a separate passage to at least one nozzle ( 9, 10, 11 ).

BACKGROUND OF THE INVENTION

The present invention relates to a spraying head as defined in thepre-amble of claim 1, especially for the humidification of the intakeair of a piston engine, said spraying head comprising a body and achannel for the supply of a spraying medium from an inlet to at leastone nozzle.

The exhaust gases of piston engines, in particular diesel engines,contain many kinds of noxious combustion products. At the highcombustion temperatures, the combustion process in the cylinders of apiston engine produces nitrogen oxides (NOx), which are emitted togetherwith the exhaust gases into the atmosphere. Because of the harmfulenvironmental effects of nitrogen oxide emissions, efforts areundertaken to minimize their production.

As is known, adding water to the combustion process reduces thegeneration of nitrogen oxides. This phenomenon is based on the coolingeffect of water. In practice, the introduction of water into thecombustion process is often implemented by injecting water into theintake air. These arrangements are advantageous in respect of efficiencyof the engine. The maximum amount of water introduced into thecombustion space of the engine may be that amount which will remain ingaseous form in the intake air pressure and temperature conditions.

The object of the invention is to achieve a completely new type ofspraying head that allows the intake air to be humidified in a desiredmanner in different engine load conditions.

Spraying head of the invention is characterized in that the sprayinghead is provided with at least two channels, each one which forms aseparate passage to at least one nozzle.

The spraying head of the invention is additionally characterized by whatis stated in claims 2-10.

The solution of the invention has numerous significant advantages. Byforming several liquid feed channels in the spraying head, it will beeasy to control the amount and/or quality of water to be suppliedthrough the spraying head. By providing the spraying head with nozzleshaving different properties, the characteristics of the water mist to beinjected can be varied in a desired manner by opening and closing themedium channels leading to different nozzles in the spraying head.Installing the spraying head as a complete module is easy as comparedwith mounting several separate nozzles. In addition, the aimingdirection of the nozzles of the spraying head and the distances betweenthem can be easily adjusted to the designed settings. Moreover, thespraying head can be securely mounted in the air intake duct. Using thespraying head of the invention, diverse adjustment possibilities and,when necessary, a good water distribution through the air intake ductare achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in detail by the aidof an example with reference to the attached drawing, wherein

FIG. 1 presents an apparatus employing a spraying head according to theinvention,

FIG. 2 presents a spraying head according to the invention, sectionedalong line II-II in FIG. 3,

FIG. 3 presents a spraying head according to the invention,

FIG. 4 presents a spraying head according to the invention installed,

FIG. 5 presents an embodiment of the invention sectioned along line V-Vin FIG. 4,

FIG. 6 presents another embodiment of the spraying head of theinvention,

FIG. 7 presents the spraying head of the invention as seen fromdirection VII in FIG. 6, and

FIG. 8 presents a section through the spraying head in FIG. 6, takenalong line VIII-VIII.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 presents a diagrammatic representation of an apparatus employingthe spraying head of the invention, installed in connection with the airintake duct 2 of a piston engine, such as a diesel engine. In thefigure, the air intake duct 2 and the exhaust duct 3 are shown in asimplified form. The engine presented in the figure is provided with asupercharger 4, which feeds air under positive pressure into the intakeduct-work 2 of the engine. To reduce the nitrogen oxide emissions of theengine, the air intake ductwork is provided with at least one sprayinghead 6, 7, fitted to feed water mist into the intake ductwork 2. In thecase illustrated in the figure, the intake ductwork is also providedwith a heat exchanger element 5, such as a charge-air intercooler. Inthis figure, two spraying heads 6, 7 are used.

At least one spraying head 6, 7 in the spraying apparatus is connecteddirectly to the structures 4 of the air intake duct 2 and a fine mistproduced by the spraying head 6, 7 comprising at least one nozzle isinjected directly into the intake air in the air intake duct. When thesolution of the invention is used, no extra chambers or other containersare needed in the air intake ductwork. The nozzles feed water mist undera high pressure into the air intake duct. The water is in the form of afine mist. Preferably 90% of the water volume (Dv90) is in the form ofdroplets having a size typically below 200 micrometers, preferably below100 micrometers and more preferably below 50 micrometers. In a typicalcase according to the invention, the pressure in the supply pipe istypically at least 10 bar, preferably at least 30 bar, most preferablyover 50 bar. The pressure range is typically 10-300 bar.

The apparatus comprises means for delivering an aqueous liquid to thenozzles. In the embodiment presented in FIG. 1, the apparatus comprisesa liquid source 21, from where the liquid is pumped through a pipe 17 bymeans of a pump 25. The pump is operated by a drive 16. The liquid canbe directed via channels 18, 19 to different nozzles 6, 7. The apparatuscomprises a system required for the regulation of the amount of watersprayed, by means of which system the amount of water to be evaporatedinto the intake air and the cooling of the intake air can be controlled.The apparatus comprises valve elements 13, 14 ar-ranged in connectionwith the liquid flow passages, such as pipes 18, 19 leading to thenozzles of the spraying head. The valves 13, 14 are typically controlledby a control system 20. Thus, the liquid flow passages 18, 19 can beopened and closed as necessary.

A spraying head 6 according to the invention is presented in FIGS. 2 and3. The spraying head comprises a body in which is formed at least onechannel 18, 18′, 18″ for conveying a pressure medium to the nozzles 9,10, 11. In the spraying head presented in the figure, a separate channel18, 18′, 18″ is provided for each nozzle 9, 10, 11. This allowsindividual control of the flow and/or pressure of the pressure mediumsupplied to each nozzle 9, 10, 11.

According to another embodiment, the nozzles of the spraying head can bearranged in groups so that each feed channel communicates with severalnozzles.

The nozzles 9, 10, 11 in the spraying head 6 may have differentproper-ties, which have been adapted according to the placement of eachnozzle. The form of the spraying head, the number of nozzles and theiraiming direction may vary depending on the application. Typically, atleast that part of the spraying head which extends inside the spacede-fined by the air intake duct walls 2 has been made narrower in thedirection of the intake air flow than in a direction perpendicular tothe direction of intake air flow. FIGS. 4 and 5 illustrate a sprayinghead of the invention mounted in an air intake duct 2. The direction ofintake air flow is indicated by an arrow in FIG. 4. Placed on the intakeair entry side, the spraying head has two nozzles 10, 11 and one nozzle9 on the exit side. The nozzles on the entry side are aimed in adirection substantially against the flow of the intake air. They mayalso differ by an angle β from the flow direction. The nozzle sprayingsubstantially in the flow direction may differ from the intake air flowdirection by an angle α. The nozzles may be aimed in a directiondeviating from at least one vertical plane by an angle c. The anglesdepend on the embodiment, such as the intake air flow rate and shape ofthe intake ductwork, so their direction and magnitude may varyconsiderably from case to case. Angles α and β may vary between 0-90°.Angle c may vary between 0-±90°.

It is also possible supply different mediums, such as water and gas, tothe nozzle. The nozzles are not shown in detail in the figure, but theymay be replaceable depending on the application.

The nozzles are therefore of a type such that they produce a spray offine mist when supplied with liquid under a high pressure. Many kinds ofnozzles of this category are known, e.g. from fire extinguishingtechnology employing water mist. For example, specifications WO 92/20454and WO 94/06567 disclose nozzles that produce a water mist at a highpressure. Naturally, other types of nozzles may also be used, e.g.specification WO 01/45799 discloses yet another nozzle.

The amount of water supplied through the nozzles typically increaseswith increasing engine load. Thus, when the engine load is low, it ispossible to supply water only to some of the nozzles and increase thenumber of nozzles spraying when the load increases. Similarly, thespraying head can be provided with nozzles having different properties,such as nozzle aperture size, droplet size produced by the nozzle, etc.It is thus possible to form different combinations which can be adaptedto a wide range of different applications, different engine types,different placements and conditions.

FIGS. 6-8 present another embodiment of the spraying head 6 of theinvention. The spraying head is arranged to extend substantially acrossthe air intake duct between the opposite walls 2-2′ of the duct. Thebody of the spraying, head preferably has the shape of a wing-likeobject. Formed in the body are channels 18, 18′, 18″ for supplying a tothe nozzles 9, 9′, 10, 11 a medium to be sprayed. In the embodimentillustrated in the figure, three inlets 29, 30, 31 into the feedchannels are provided at the first end 70 of the spraying head. Oneinlet 29 is provided at the opposite end 71 of the spraying head. Thenozzles are arranged to spray in desired directions. In the embodimentillustrated, some of the nozzles 9, 10, 9′ are arranged to spray in theair intake duct against the direction of air entry while some of thenozzles 11 are arranged to spray in the direction of air flow. Nozzles9, 9′ and 10 are therefore placed at the edge 74 of the spraying headbody facing against the air entry direction while nozzles 11 are placedat the air exit-side edge 75 of the body. Formed in the body of thespraying head are three channels 18, 18′, 18″ coming from the first endof the spraying head and one channel 18′″ from the second end of thespraying head. With the spraying head of the invention, the spraying ofthe pressure medium to be sprayed can thus be distributed over the widthof the air intake duct at least in the area of the spraying head. Inaddition, by directing the supply of pressure medium to differentchannels 18, 18′, 18″, 18′″, it is possible to influence the operationof the spraying head feeding the air intake duct in respect of e.g. thedirection of injection or the point of injection. For example, thespraying can be implemented by initially spraying by the nozzles 10 inthe middle, next by also spraying by the nozzles 9, 9′ in the edge part,either from one edge or both edges, and finally by spraying by thenozzles 11 at the exit-side edge as well.

Provided at the first end of the spraying head is a mating surface 73which is pressed against the wall 2 of the air intake duct eitherdirectly or via an intermediate piece. Formed or arranged at theopposite end 71 of the spraying head is a supporting element extendingto the opposite side of the opposite wall 2′. The supporting elementtypically is pro-vided with threads allowing the spraying head tomounted and tightened on the air intake duct by means of a fasteningelement, such as a nut. The spraying head according to this secondembodiment is typically mounted in an opening formed in the wall 2 ofthe air intake duct, said opening having dimensions such that thespraying head parts intended to go inside the air intake duct can beinserted through it. The shape of the opening is typically designed thatit also guides the spraying head to the correct position in the airintake duct. Formed in the opposite wall 2′ of the air intake duct is asecond opening, which is so designed that at least the supportingelement 76 can go through it while a second mating surface 77 formed atthe other end of the spraying head remains inside the air intake duct.The spraying head is locked on the air intake duct by means of a nutprovided on the supporting element 76 so that the other wall 2′ remainsbetween the second mating surface and the tightening element (notshown). This arrangement allows the spraying head to be easily andsecurely mounted on the air intake duct.

FIG. 8 presents a cross-sectional form of the spraying head presented inFIG. 6. That part of the spraying head which is to go inside the airintake duct is preferably formed as a wing-shaped part. In itscross-sectional form, it has a thicker portion at the middle, becomingthinner towards the edges 74, 75. In the case presented in the figure,the cross-sectional form is symmetrical, but it need not necessarily besymmetrical. The cross-sectional form can be adapted according to theapplication.

An apparatus employing the spraying head of the invention can fullyutilize the quantity of heat required for the vaporization of water,cooling the intake air at each injection point to a temperature close tothe wet bulb temperature (or adiabatic saturation temperature, which inthe case of a water-air mixture is practically the same thing), i.e. tothe temperature to which the temperature of air can be reduced byvaporization of water.

In the apparatus of the invention, the humidity of the intake air ispreferably increased stepwise after each heat supply point. However,relative to the direction the intake air flow, water mist is injectedbefore the last heat supply point, which can be used as a waterevaporation surface.

By this arrangement, the humidity of the gas fed into the cylinder andtherefore the formation of nitrogen oxides is regulated within thede-sired limits.

It is obvious to the person skilled in the art that the invention is notlimited to the example described above, but that it may be varied withinthe scope of the claims presented below. Thus, the spraying head maycomprise two, three, four or more nozzles. The spraying head has atleast two channels.

1. Spraying head for the humidification of intake air, especially the intake air of a piston engine, said spraying head comprising a body and a channel for supplying a spraying medium from an inlet to at least one nozzle, characterized in that the spraying head (6) is provided with at least two channels (18,18′,18″), each forming a separate passage to at least one nozzle (9,10,11).
 2. Spraying head according to claim 1, characterized in that at least some of the nozzles (9,10, 11) of the spraying head are different from each other.
 3. Spraying head according to claim 1, characterized in that a shutting/regulating mechanism is provided in connection with the spraying head (6) to allow the supply of medium to the channels (18,18′, 18″) leading to different nozzles to be shut off/regulated.
 4. Spraying head according to claim 1, characterized in that the nozzles (9,10,11) have been adapted for spraying a liquid mist.
 5. Spraying head according to claim 1, characterized in that the spraying head has been adapted for spraying a high-pressure liquid mist.
 6. Spraying head according to claim 1, characterized in that the nozzles (9,10,11) are arranged in groups, and that at least one channel (18,18′, 18″) leads to each one of said groups.
 7. Spraying head according to claim 1, characterized in that the spraying head comprises at least one nozzle (9) arranged to spray in a direction substantially against the direction of flow of the intake air.
 8. Spraying head according to claim 1, characterized in that at least some of the nozzles (9,10, 11) are arranged to spray in a direction substantially in the same direction.
 9. Spraying head according to claim 1, characterized in that the spraying head comprises at least one nozzle (10,11) arranged to spray substantially in the direction of flow of the intake air.
 10. Use of a spraying head according to claim 1 in the humidification of the intake air of a piston engine. 